How did our preferences change from our familiar bikes with mid-trail geometries, 700C x 28 mm tires and saddlebags to low-trail 650B bikes with much wider tires and handlebar bags? In the previous parts of this series, we related how we found out about the advantages of handlebar bags, aluminum fenders, and supple, wide tires.

Then we discovered how much difference front-end geometries can make. Both Mark and I had ridden tens of thousands of miles on bikes with “mid-trail” geometries – about 55 mm trail with 700C x 28 mm tires. In 1999, we each had custom bikes made with that geometry, because at the time, we felt that they offered the best handling we had experienced on a bike. When an American bicycle maker asked Bicycle Quarterly about ideas for the perfect randonneur bike, I talked at length about lights and racks. When the maker asked about geometry, I replied: “Your slightly relaxed geometry probably is just about perfect for a randonneur bike.”

Then I started riding an old Alex Singer randonneur bike (see above) once in a while. The Singer surprised me: “Tricky” corners suddenly were less difficult. When I noticed a pothole too late, and thought that I would not be able to steer around it, I braced myself for the impact. To my surprise, the bike responded quickly enough to avoid the pothole. When I got tired, the Singer was easier to keep on a straight line – in fact, I could ride on the white painted “fog line” for miles with little concentration (see photo at the top of the post). Riding no-hands at moderate speeds was easier, too. This confused me: The Singer had “quicker,” more precise steering, yet it was more stable.

When I switched back to my normal bike after a single ride on the Singer, I found myself running wide in corners. I hit potholes that I thought I would miss. And the bike sometimes weaved unexpectedly when I was getting tired. Both bikes had a similar positions, both had handlebar bags, but something was different. To my surprise, the bike I rode all the time felt less intuitive than the new-to-me Singer.

That is when we started measuring geometries. We realized that the Singer’s geometry was anything but the “relaxed” geometry we had expected. The bike had a steep head angle and less trail than was common at the time.

During Mark’s first ride on my Singer, over a challenging stretch of road, he exclaimed: “Now I know how a bike should handle.” We both immediately preferred the “optimized” bike over the ones we usually rode.

This raises an interesting question: Is habituation stronger than optimization? Will a rider just prefer the bike they usually ride, or is there an “optimum” setup that will appear superior even to those who are not used to riding it? Based on our experiences with front-end geometry, we prefer “optimimized” bikes over those we usually ride.

I began riding the old Singer more and more, until it had replaced my usual bike. And Mark ordered a new custom bike altogether.

Mark’s new bike was designed around the Mitsuboshi 650B x 38 mm tires that I had used in the 2003 Paris-Brest-Paris. It used the geometry of the 1952 René Herse that I had liked so much. Of course, Mark’s new bike was equipped with a handlebar bag and aluminum fenders. And by now, we also had discovered that we did not need very large gears. The “compact doubles” used on many classic randonneur bikes allowed us to ride most terrain in the big chainring, thus eliminating many front shifts.

Mark initially intended his new bike as a special bike for fast events. He planned to use his old bike on gravel roads, for touring and many other rides. In the end, he preferred his new bike so much that he rode it all the time. He even made a low-rider rack for it, so he could take it touring.

So by 2005, our “best bikes in the world” had been replaced by a 1973 French Alex Singer and by a modern bike inspired by a 1952 René Herse. But our journey of discovery was not yet over…

23 Responses to A Journey of Discovery, Part 4: Front-End Geometry

Thanks for this great series. I’ve learned a lot from this blog and from Bicycle Quarterly. One question. How would a frame builder build such a bike as you describe for someone who it tall? Many builders seem to prefer 650b tires for average sizes, but when frames get larger, say 62cm and up, they all seem to recommend or build 700c frames. Can a 650b bike work for those of us who need a big frame?

I have a related question. It seems that you and Mark both ride rather large frames. How does rider/frame size interact with preferred trail? Does your need for a bigger bike bias (I don’t mean this in a pejorative sense) your front end geometry preferences?

It’s hard to see why front-end geometry should change much based on rider height. Obviously, you may need to slacken the head angle a bit for very small frames to avoid toe overlap… Both Mark and I are 183 cm (6′) tall, so we are not that far from the average American male in height.

The whole issue of scaling bikes up with rider height is interesting. If you want to keep the weight distribution the same, you need to increase chainstay length as the front-center goes up. Furthermore, as you point out, taller riders have a higher center-of-gravity. Does this mean that taller riders cannot turn corners as tight as smaller riders? Do we see smaller racers out-descend taller ones in professional races? I don’t think so, unless the smaller riders also are heavier.

Years ago, Peter Weigle sent us a test bike years ago, with the same the front-end geometry as a 1954 Alex Singer. Peter visited while we tested the bike. We rode the Singer and the Weigle back-to-back. Both handled the same – neither Peter nor I could detect a difference. However, Peter’s bike had chainstays that were 450 mm long, whereas the Singer’s were 430 mm. In terms of chainstay length, that is a big difference, yet we could not detect it. It appears that these differences don’t make a huge difference in how the bike handles.

More important is your riding position. If you sit more upright, you have less weight on the handlebars, thus less wheel flop, and so you should have more trail. Perhaps shorter riders also put less weight on the handlebars (their upper bodies are lighter), so you might increase the trail a little bit. Most likely, this effect is too small to make a huge difference.

Is there something inherent in the 650b wheels that gives the older bikes the handling characteristics you so admired? Do you think the ride could be replicated with larger (35mm and up) tires on 700c wheels, coupled with appropriate frame and fork geometry?

Gyroscopic stability is a crucial factor in bicycle handling. We haven’t found a way to compensate for that by changing trail, fork offset or head angle. Neither have motorcyclists – they changed their wheel sizes (smaller for wider tires, then larger again when low-profile tires became popular). Thus, you cannot make a 700C x 38 mm tire/wheel handle the way a 650B x 38 mm tire/wheel does. See also our test of three wheel sizes. On the other hand, 650B wheels don’t handle so great with tires narrower than 30 mm…

Hi Jan,
Very interesting series! I had wondered how you had come to study the front end geometries on French randonneur bikes. It’s interesting that at the beginning of the 21st century we in America are re-discovering what other American cyclists had know in the 50’s and 60’s! I’m referring to Dr. Graves who rode Rene Herse bicycles at that time as well as others. (See p. 131, The complete book of bicycling, 1970 by Sloane or p. 7 of DeLong’s guide to bicycles & bicycling.) Some how that information was lost or dismissed by later cyclists.
Tom

What advice would you offer to someone who would like to try a bike with low trail? At the moment, there really isn’t any way to get one, other than spending a great deal of money on having one custom made – which would be huge leap of faith!

The best option is to buy a used bike. There are a couple of hundred Kogswell P/R out there. Just make sure you measure the fork offset, as some of those forks were mis-shipped, and aren’t what their owners ordered… If you don’t like it, you can sell it for what you paid approximately. The biggest problem is that the owners of these bikes seem to like them – they don’t come up for sale often.

The second option is to take an existing bike and either have the fork re-raked, or have a new one built. As long as your bike has a head angle of 72-74 degrees, this is an easy option. It also increases your front-center, which can be a good thing if your bike has toe overlap. At the same time, you may be able to incorporate a good rack, so your handlebar bag has good support…

The third option is to carefully examine our articles on front-end geometry. If the evidence is convincing, talk to people who have the aforementioned bikes. Then, take the “leap of faith” and buy a new bike with an optimized geometry. There are a few production bikes now with geometries like that (Boulder Bicycles, Box Dog Pelican), and if, against the odds, you don’t like it, resale values for these tend to be high, so your loss would be small.

Perhaps the most important thing is to get the geometry right, based on tire size, load you plan to carry, etc.

Jan, your comments about the Singer’s surprising stability and your later response regarding the influence of rider position on trail raises two questions for me.

1. How much is a rider who only occasionally exceeds 20 km/h during rides of 100-130 km really going to appreciate the handling difference of a lower-trail bike? (Assuming that the rider’s usual higher-trail bike is loaded appropriately for its design, etc.)

2. Have you quantified the influence of front loads (or luggage loads in general) on trail? More generally, to what degree are mechanical trail, pneumatic trail, load distribution, and rider position independent variables in the handling of the bike? Put another way, could one theoretically reproduce the handling of a low-trail, 650Bx42-equipped, front-loaded bike with the proper configuration of higher trail, 700c (or 26 in) tires, and load and rider positions?

1. The advantages of lower-trail bikes are most pronounced at lower speeds, because these bikes have less wheel flop. Most bikes handle great once you exceed 40 km/h (except in cross-winds, where more trail gives the wind more leverage on the bike’s steering).

2. We have done a lot of research on these factors. You can make a 55 mm-trail bike handle very nicely with a saddlebag and 28 mm tires. That is how my “best bike in the world” started out. However, when you rise out of the saddle, you will get the “tail wagging dog” effect. And most of all, you cannot get to your stuff while riding.

Forgive me I have not read (but will) all of your literature on gyroscopic affect. I am “stuck” with a 700c Heron Wayfarer, with 35c tires. Something I noticed about the Gyroscopic wheel chart, was that it’s not just tire size, but weight that matters. Thus, wouldn’t a 330 gram Schwalbe Marathon Racer have the same gyroscopic affect as a 28 or 32c tire that has a wire bead, weighing same as the lightweight Schwalbe Racer?

Absolutely. When we tested the gyroscopic effects, we used both lightweight tires (Grand Bois) and heavy tires (Schwalbe Marathon). Wheel size has the biggest influence on gyroscopic stability. Tire weight comes second. Tire width plays a minor role, as it impacts the effective wheel size. When you use a tire width that falls between wheel sizes for optimum handling, we recommend going to the smaller size if you use heavy tires, and to the larger size if your tires are lightweight. So a heavy 32 mm tire would work best with 650B, but a lightweight 32 mm tire would offer the same “optimized” handling with a 700C wheel.

>This raises an interesting question: Is habituation stronger than optimization?

Not in my experience.

I’d ridden either racing bikes and bikes designed around rear loading strategies my adult life. When I started randonneuring in 2004, the advantages of a handlebar bag for self-supported riding (nosebag, wardrobe, and map-case right at hand. No need to stop to change clothes, eat, or figure out where I was/where I was headed) became evident, as did the limitations of a racing/rear-loading touring bike when equipped with a handlebar bag. My first ride with a handlebar bag was a 400K on a Heron Touring model, and that bike, previously a mild-mannered machine, dove for the ditches with a vengeance. I removed the handlebar bag and stuffed it into my saddlebag, and the handling problem went away (but I got lost, bonked, and had to stop to change clothes, among other problems).

Shortly thereafter, I ordered an Alex Singer blind, and the handlebar bag went from being a randonneuring ergogenic aid added at the expense of the machine’s handling to something worth designing a custom machine around. The handling with a light front load was a revelation–and it was apparent from the first few miles on the bike.

Concerning the handling, I can’t recall being passed on a downhill while riding one of my low-trail randonneuring machines in seven years riding on the Colorado Front Range, and it is easy to change out of a jacket and legwarmers while tootling along no-hands on the flats, and I’m neither a daredevil nor an acrobat on the bike.

Sorry, Jan, let me correct myself about tire weights. Looking at the chart on pg. 69 of the latest issue of Bicycle Quarterly, the heaviest tire still within the optimal zone for 700c rims, is the 32mm (30mm actual) Pasela TG @ 360g. According to the Schwalbe website, the 35c Marathon Racer w/ folding bead weighs 360g also. I’m not sure of the actual size, but I think I can assume it’s wider than the 32mm Pasela, making it a better choice for someone that favored a cushier tire, yet limited by 700c wheel size.

Of course, here in Chicago the roads are so straight and flat, it’s probably just as well to go with a large heavy tire with kevlar puncture protection, to provide plenty of gyroscopic force to keep you upright after rolling through all the ever present potholes!